Electric discharge device



Aug. 3l, 1937. T. A. ELDER ELECTRIC DISCHARGE DEVICE Filed May 4, 1935 Pfg. z.

Illlnlfdlfnnlfff Inventor Thomas Afldef,

Hls A torney.

Patented Aug. 31, 1937 UNITED STATES Zgil AParar oFrlcE ELECTRIC DISCHARGE DEVICE Thomas A. Elder, sentia, N. assigne-r to General Electric Company, a corporation of New York Application May 4, 1935, Serial No. 19,867

Claims.

f5 means for regulating the pressure of the ionizing medium.

The ability of rectiers and controlled discharge tubes which contain mercury or a similar ionizing medium to withstand inverse voltages is largely dependent upon the vapor pressure of the medium. For this reason it is particularly important in all-metal tubes, whose walls tend to run at a uniformly high temperature, that some means be provided for continuously condensing a portion of the vapor content. In the past it has been regarded as necessary to accomplish this result by increasing the size of the tube envelope until a state of thermal equilibrium has been reached at which the heat generated by the cathode and arc stream cannot keep the vapor pressure above a predetermined limit.

My invention provides a cooled external storage space for the ionizing medium which is connected with the interior of a metal discharge envelope by a tubulation of relatively low thermal conductivity projecting from a metal wall portion of the envelope. I have found that it is possible in this way to regulate to any predetermined degree the vapor pressure existing in the envelope.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims and will be ,fully understood upon reference to the following specification and drawing in which Fig. 1 is a ,vertical section of a metal tube embodying my invention; Fig. 2 is a detailed sectional View showing a preferredembodiment of my invention, While Fig. 3 is a section taken on line 3-3 of Fig. 2. Fig. 4 shows a practical modification of the cooling structure, and Fig. 5 is a sectional view taken on line 5-5 of Fig. 4.

yReferring more particularly to Fig. 1, I have illustrated a metal envelope I comprising a section of seamless steel tubing and adapted to enclose discharge producing electrodes. This is closed at the top by a metal diaphragm or header 2 provided with a circumferentially extending ange of such diameter as to t the internal peripheral surface of the envelope I. An hermetic seal is obtained between these two parts by line welding or other suitable fusion methods. The envelope I, which in the embodiment illustrated serves as an anode encloses a cathode member 3, which is illustrated as a pleated metal ribbon of vnickel or other temperature resisting metal, coated exterorly with an electronically active material such as barium oxide. The cathode 3 is supported between current conductors I and 5 joined at their lower extremities to heavy copper rods 6 and 1.

The rods ii and l are butted on to a cooperating pair of inverted thimbles 8 and 9 of material suitable or the formation of a glass to metal seal. In this way gas-tight connections are made to external lead-in conductors Ill and II, respectively. .I A seal of this type is fully described and claimed` in application, Ser. No. 716,111, to H. J. Nolte led December 26, 1933, and assigned to the same assignee as the present invention. Since its nature is not material to the structure of my invention, it is not necessary that it be described with greater particularity.

The lead-in connections Il] and I I are supported against lateral displacement and insulated against contact with one another or with other.;4

metal parts by an insulating block I2 suitably secured to a base plate I3 which completes the hermetic closure ofthe envelope I. Also suspended from the metal base plate I3 is a heat radiating structure I4 to be described in detail hereinafter.

In Fig. 2 I have shown a tubulation I5 of steel or other ductile material fusion-welded or otherwise secured to the base plate I3. The lower extremity of the tubulation is pinched on" and.

welded to form a storage chamber Iii for a quantity of mercury or equivalent condensble ionizing material II. Whiley the storage reservoir I6 is shown as an extension of the tubulation I5, it will be apparent that a special chamber or enlargement might also be utilized for this purpose.l

The radiator It mentioned above is mounted in heat exchanging relation with that portion of the depending tubulation which acts as a storage space. In the embodiment illustrated the radiator is shown as comprising a metallic cylinder I8 of heat conducting material, such as copper, and a` plurality of channel members I9 assembled in good thermal contact therewith. The channel members are so formed that the walls of adjacent elements abut in face to face relationship forming fins projecting radially with respect to the axis of the tubulation I5. Y

The radiator structure is mounted and kept in good thermal contact with the storage chamber L I6 by means of a mass of fusible material 20 which may conveniently consist of a low melting point solder. A plug ZI of any suitable material is inserted in the bottom of the cylinder I8 as a retainer for the solder when in its molten state. i

such as using a material whose speciic heat conductivity is naturally low, or incorporating a heat insulating barrier in the wall of the tube.

By the use of a condensing reservoir for the ionizing medium constructed in accordance with the principles of my invention, it is possible to regulate the vapor pressure of the medium Within No matter what the temany desired limits. perature of the discharge envelope may be, a condensing effect can be obtained in the storage chamber by the use of a sufliciently large radiating surface.

The abundant heat generated by the arc discharge and retained in the walls of the envelope I is prevented from owing to the storage chamber by the limited conductivity of the tubulation walls. The length and cross section of the latter may be so chosen that when a state of temperature equilibrium is reached, just enough heat will be transmitted to the mercury to maintain the optimum vapor pressure in the envelope. This throttling effect is an extremely important advantage of my invention since it provides a means of preadjusting the conditions under which the discharge tube is to operate.

In Figs. 4 and 5 I have shown a modiiication of which my invention is capable. This alternative structure may be mounted in the same relation to the tube envelope as is the embodiment of Fig. 2, or may be combined in any other assembly in which the tubulation projects outwardly into a position relatively remote from the heat source. As shown, the radiator 23 comprises a pair of sheet metal vanes 24 stamped into a channel-like shape with semi-cylindrical corrugations 25 extending along their longitudinal axes. These stampings are placed in back to back relation so that the corrugations enclose and grip the tubulation 25. The exposed metal surfaces form an eiiective cooling means which can be modified at will by varying the area of the vanes 24.

I have shown the tubulation 26 as extending below the lower edge of the vanes 24. In this way it is made possible to complete the radiator assembly before the tubulation is sealed off whenever this is desirable from a manufacturing point of View. To secure the parts in place brazing, soldering or an equivalent operation may be resorted to.

It will be obvious that my invention is in no way limited to the particular cooling devices shown, and that other means of increasing the heat dissipation from the outer extremity of the tubulation may be employed. For example, it is obviously possible to increase the capacity of the discharge tube by using a circulating fluid as a means of removing heat from the condensing chamber.

I have described my invention as being particularly applicable to mercury vapor tubes, but it will be obvious to those skilled in the art that other condensible ionizing media, such as gallium or caesium, might be utilized in this connection with equal success.

While I have shown a particular application of my invention, it will of course be understood that I do not wish to be limited thereto since many modifications in the structurai arrangement may be made, and I contemplate by the appended claims to cover all such modifications as fall within the true spirit and scope of my' invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

l. A discharge -device comprising a sealed envelope consisting principally of metal, one or more electrodes within said envelope, a tubulation projecting outwardly from a metal wall portion of said envelope and containing a reserve of a condensible ionizing medium, and heat dissipating means mounted on a portion of said tubulation remote from said envelope, said tubulation being of limited heat conductivity whereby heat iow therethrough is restrained and said portion of said tubulation is maintained at a predetermined condensing temperature.

2. A discharge device comprising a sealed envelope consisting principally of metal, one o1' more electrodes within said envelope, a container outside of said envelope and enclosing a reserve of a condensible ionizing medium, a plurality of metal vanes in heat exchanging relation with said container and a tubulation projecting outwardly from a metal wall portion of said envelope and connecting said container with the interior of the envelope, the cross-sectional area of. the walls of the tubulation being a small fraction of the surface of said vanes whereby said container is maintained at a predetermined condensing temperature.

3. A discharge device comprising a sealed envelope consisting principally of metal, one or more electrodes within said envelope, a container outside of said envelope and enclosing a reserve of a condensible ionizing medium, a tubulation f projecting outwardly from a metal wall portion of said envelope for connecting said container i with the interior of the envelope, and heat dissipating means mounted on said container, the walls of said tubulation consisting at least in part of a material whose specific thermal conductivity is substantially less than that of the metal of said envelope, whereby said container is maintained at a predetermined condensing temperature.

4. A discharge device comprising a sealed envelope consisting principally of metal, one or more electrodes within said envelope, a container outside of said envelope enclosing a reserve of. a

condensible ionizing medium, cooling vanes in heat exchanging relation with said container, and means projecting outwardly from a metal Wall portion of said envelope and connecting the interior of said container with the interior of the envelope, said means being of limited heat con-y,`

THOMAS A. EIDER. 

